Typically, grillage foundations used, support various structures, for example, electrical transmission lines that are normally designed to transfer and distribute heavy concentrated loads on soil having low bearing capacity. These grillage foundations resist uplift and thrust forces that result from the self-weight of the tower and the lateral and longitudinal transmission wire loads in normal and/or broken wire conditions. In addition to such forces, the foundation also resists wind and ice loads on the tower body, the insulators, and the conductors.
The grillage foundations of the prior art consist of one or more layers of galvanized steel beams perpendicular to each other and assembled on site.
Currently, the electrical transmission industry is experiencing an increasing corrosion challenge in the galvanized steel members typically near to the ground level and underground. The fact that the grillage foundations are underground and not easily accessible for maintenance inspections, increase the risk of sudden tower failures which may cause to electrical outages. For these reasons, the existing steel grillage foundation is a less reliable solution for the electrical transmission line industry.
Moreover, the galvanized steel material used in the grillage foundations has delivery lead times of six months or longer. It is important to note that in some jurisdictions the construction window for electrical transmission lines is only four months. For this reason, ordering material with long lead times does not allow engineering to match design with real soil requirements that can only be obtained through construction season. Moreover, since the grillage foundation is a framework of galvanized steel with wide flange beams and channels, the material is shipped as separate pieces needed to be assembled on site. For this reason, labour costs become the cost factor for such steel grillage foundations.